1. Field of the Invention
This application is based on Japanese Patent Applications Nos. 2005-377867, and 2005-377868, the content of which is incorporated herein by reference.
2. Description of Related Art
The present invention relates to a projector.
Conventionally, there is known a projector arranged such that a reflective display device such as a digital micromirror device (Trademark)(DMD (Trademark)) and a collecting lens are disposed side by side in an optical axis direction, and an aperture diaphragm and an illuminating light diaphragm are disposed at the front focusing position of the collecting lens in a direction orthogonal to the optical axis (refer to, for example, Japanese Unexamined Patent Application Publication No. 8-251520). Further, there is also disclosed a projector which has no illuminating light diaphragm and has a point light source arranged by focusing an image of a lamp light source on a focusing surface of a collecting lens by collecting the illuminating light emitted from the light source (refer to, for example, Japanese Unexamined Patent Application Publication No. 8-201755).
Further, there is conventionally known a projector arranged such that the light from a light source apparatus such as a xenon lamp and the like is caused to pass through a display device such as a transmissive liquid crystal panel or is reflected by a reflective display device such as a digital micromirror device (Trademark) so that light is overlapped with an image signal and then an image is projected through a projecting lens (refer to, for example, Japanese Unexamined Patent Application Publication No. 2001-249400).
In these projectors, basically, the illuminating light from a point light source, which is formed by collecting the light from a lamp light source by an elliptic mirror and an optical system, or the illuminating light from a point light source, which is formed by an illuminating light diaphragm disposed at the focusing position of an elliptic mirror, is deflected by a mirror so that the illuminating light is incident on a collecting lens. Accordingly, the mirror disposed on a light path of the illuminating light must have a size and a position which do not shut off the light outgoing from an aperture diaphragms disposed on a focusing surface in juxtaposition.
However, there is a disadvantage in that since a relatively large mirror must be disposed actually, a relatively large interval must be secured between the illuminating light diaphragm and the aperture diaphragm or between the image of the lamp light source and the aperture diaphragm.
That is, when the interval is increased, the amount of decentration of the optical axis of the illuminating light which is incident on and outgoes from the collecting lens increases, which is disadvantageous in that aberration is increased. Further, there is also a drawback in that the diameter of collecting lenses disposed at intervals along an optical axis must be increased to retrieve the illuminating light which is incident on and outgoes from the collecting lens as much as possible.
Further, when it is intended to obtain a point light source having high brightness using a lamp light source, there is also a disadvantage in that since the lamp light source is increased in size as well as accessories such as a cooling fan and the like for suppressing heat generated by the lamp light source are also increased in size, a projector is increased in size in its entirety.
Further, since the light source apparatus such as a xenon lamp and the like are placed in a high temperature state as described above due to the heat generated thereby, they must be forcibly cooled by a cooling fan and the like. Accordingly, there is a drawback in that the sound generated by the cooling fan when it is driven in rotation is noisy. Further, hot air is discharged from the light source apparatuses to the outside by the cooling fan.
Accordingly, in a small and closed looking/listening space such as a vehicle compartment, a problem arises in that the S/N ratio of sound of images is greatly increased by the noise of the cooling fan, and further the temperature of the compartment is increased by the hot air discharged from the fan. Further, since the projector includes components occupying a relatively large space, for example, the lamp such as the xenon lamp and the like of the light source apparatus, the cooling fan, and the optical system including lenses and the like, there is also a problem in that the projector is increased in size and thus it is difficult to dispose it in the small looking/listening space.